Rep protein as protein antigen for use in diagnostic assays

ABSTRACT

Disclosed is a method of diagnosing multiple sclerosis (MS), wherein a blood sample from a patient is incubated with a DNA-replication associated (REP) protein. The present invention relates to a DNA-replication-associated (Rep) protein for use in the diagnosis of multiple sclerosis (MS), wherein (a) an increased amount of Rep protein or fragments thereof in the sample as compared to an amount in a control sample; or an increased amount of anti-Rep protein antibodies with antigen in a sample from a subject as compared to an amount in a control sample correlates with a diagnosis of MS, wherein the Rep protein is MSBI1 Rep or MSBI2 Rep.

RELATED APPLICATIONS AND INCORPORATION BY REFERENCE

This application is a continuation of U.S. patent application Ser. No.16/376,154 filed Apr. 5, 2019, now allowed, which is acontinuation-in-part application of international patent applicationSerial No. PCT/EP2017/075774 filed 10 Oct. 2017, which published as PCTPublication No. WO 2018/069296 on 19 Apr. 2018, which claims benefit ofEuropean patent application Serial No. 16193119.1 filed 10 Oct. 2016.

The foregoing applications, and all documents cited therein or duringtheir prosecution (“appln cited documents”) and all documents cited orreferenced in the appln cited documents, and all documents cited orreferenced herein (“herein cited documents”), and all documents cited orreferenced in herein cited documents, together with any manufacturer'sinstructions, descriptions, product specifications, and product sheetsfor any products mentioned herein or in any document incorporated byreference herein, are hereby incorporated herein by reference, and maybe employed in the practice of the invention. More specifically, allreferenced documents are incorporated by reference to the same extent asif each individual document was specifically and individually indicatedto be incorporated by reference.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has beensubmitted electronically in XML format and is hereby incorporated byreference in its entirety. Said XML copy, was created Jun. 15, 2023 andis named Y8005_01017SL.xml and is 23,475 bytes in size.

FIELD OF THE INVENTION

The invention relates to the detection and quantification of aDNA-replication-associated (Rep) protein or anti-Rep antibodies for usein the diagnosis of a neurodegenerative disease such as, for example,multiple sclerosis (MS). In particular, the invention relates to a MSBI1genome-encoded Rep protein.

BACKGROUND OF THE INVENTION

The etiology of multiple sclerosis (MS) has not been resolved. Thus,there is a demand for a biomarker for MS which could be used fordiagnosing MS and/or monitoring MS or a treatment of MS and/or assessinga predisposition for MS.

Multiple sclerosis (MS) is characterized by demyelinization of MSlesions damaging nerve cells in the brain and spinal cord. MS symptomseither occur as episodes of sudden worsening (relapses, exacerbations,bouts, attacks) or as a gradual worsening over time (progressive forms).Demyelinization starts inflammatory processes which trigger T cells andthe release of cytokines and antibodies. For the diagnosis of MS, amongothers, neuroimaging, analysis of the cerebrospinal fluid and evokedpotentials are used.

A spectrum of 17 different, but partially related DNA molecules wereisolated from different test material (multiple sclerosis (MS) braintissue, bovine sera, milk) (Funk, Gunst et al. 2014, Gunst, Zur Hausenet al. 2014, Lamberto, Gunst et al. 2014, Whitley, Gunst et al. 2014).

Among these isolates two DNA molecules closely related to transmissiblespongiform encephalophaty (TSE)-associated isolate Sphinx 1.76 (1,758bp; accession no. HQ444404, (Manuelidis L. 2011)) were isolated frombrain tissue from MS patients. These isolates were MSBI1.176 (MSBI,multiple sclerosis brain isolate) (1,766 bp) and MSBI2.176 (1,766 bp)which are designated as “MSBI1 genome” and “MSBI2 genome”, respectively.MSBI1,176 shares 98% nucleotide similarity to the sequence of Sphinx1.76. The large open reading frames (ORFs) of the isolates encode aputative DNA replication protein sharing high similarity between them.Another common feature is the presence of iteron-like tandem repeats.The alignment of this repeat region indicates a variation in the core ofsingle nucleotides. This iteron-like repeats may constitute the bindingsites for Rep proteins. The sequences of the isolates have beendeposited in the EMBL Databank under accession numbers LK931491(MSBI1.176) and LK931492 (MSBI2.176) (Whitley C. et al. 2014) and havebeen aligned and described in WO 2016/005064.

Further isolates were obtained from cow milk. These Cow milk isolates(CMI) were CMI1.252, CMI2.214 and CMI3.168 which are designated as “CMI1genome”, “CMI2 genome” and “CMI3 genome”, respectively. The sequences ofthe isolates have been deposited in the EMBL Databank under accessionnumbers LK931487 (CMI1.252), LK931488 (CMI2.214) and LK931489 (CMI3.168)and have been aligned and described in WO 2016/005064.

Citation or identification of any document in this application is not anadmission that such document is available as prior art to the presentinvention.

SUMMARY OF THE INVENTION

The present inventors have found that MSBI1 genome shows a significantproduction of transcribed RNA and MSBI1 genome-encoded Rep protein isexpressed in human cells. The present inventors have found that theMSBI1 and MSBI2 genome-encoded Rep protein (MSBI1 Rep and MSBI2 Rep)represent a biomarker for pathogenicity screening assays. AsDNA-replication-associated protein (RepB) the Rep protein has DNAbinding activity and can be essential for initiation of replication ofepisomal or viral DNA molecules. Rep proteins, which are structurallysimilar to the MSBI1 genome-encoded Rep according to the presentinvention, show a marked potential of self-oligomerization andaggregation, which was described within prokaryotic systems in vivo andin vitro (Giraldo, Moreno-Diaz de la Espina et al. 2011, Torreira,Moreno-Del Alamo et al. 2015).

The present invention provides a platform for pathogen-specific,diagnostic screening assays based on the use of a Rep protein as anantigen.

In certain embodiments anti-Rep antibodies are used as pathogenicmarkers due to the link of pathogenic activity of the isolated DNA (e.g.MSBI1) agent with the Rep protein expression. Patient sera containingincreased amounts of anti-Rep antibodies indicate that the correspondingpatient was definitely exposed to Rep-related proteins or himselfexpressed Rep during a time period long enough to initiate a Repspecific immune response. As target for the human antibodies Rep proteinis used as the antigen. Based on the quantification of the amount ofanti Rep antibodies acute MS as well as a predisposition for MS can bediagnosed or monitored. Because it has been recognized that increasedamount of induced anti-Rep antibodies or expressed Rep protein in asample indicates the onset and/or status of MS, the increased amount ofanti-Rep antibodies and Rep protein, respectively, can be used aspathogenic biomarker for the diagnosis of MS.

Advantageously, the pathogenic biomarker for MS can be detected in bloodsamples, such as serum or plasma samples, and it is not necessary toobtain samples from the cerebrospinal fluid.

Hence, the invention provides a DNA-replication-associated (Rep) proteinfor use in the diagnosis of a neurodegenerative disease, for example,multiple sclerosis (MS). In certain embodiments, the Rep protein isencoded by the MSBI1 genome and may comprise (i) an amino acid sequenceas depicted in SEQ ID NO:1; (ii) a fragment of SEQ ID NO:1 which iscapable of binding an anti-Rep antibody specific for a protein which maycomprise an amino acid sequences as depicted in SEQ ID NO: 1; or (iii)an amino acid sequence having a 90% or more homology to the amino acidsequence of (i) or (ii) and is capable of binding an anti-Rep antibodyspecific for a protein which may comprise an amino acid sequences asdepicted in SEQ ID NO: 1.

In other embodiments the Rep protein is encoded by the MSBI2 genome andmay comprise (i) an amino acid sequence as depicted in SEQ ID NO:8; (ii)a fragment of SEQ ID NO:8 which is capable of binding an anti-Repantibody specific for a protein which may comprise an amino acidsequences as depicted in SEQ ID NO: 8; or (iii) an amino acid sequencehaving a 90% or more homology to the amino acid sequence of (i) or (ii)and is capable of binding an anti-Rep antibody specific for a proteinwhich may comprise an amino acid sequences as depicted in SEQ ID NO: 8.

In other embodiments the Rep protein is encoded by the CMI1 genome andmay comprise (i) an amino acid sequence as depicted in SEQ ID NO:10;(ii) a fragment of SEQ ID NO:10 which is capable of binding an anti-Repantibody specific for a protein which may comprise an amino acidsequences as depicted in SEQ ID NO: 10; or (iii) an amino acid sequencehaving a 90% or more homology to the amino acid sequence of (i) or (ii)and is capable of binding an anti-Rep antibody specific for a proteinwhich may comprise an amino acid sequences as depicted in SEQ ID NO: 10.

In other embodiments the Rep protein is encoded by the CMI2 genome andmay comprise (i) an amino acid sequence as depicted in SEQ ID NO:11;(ii) a fragment of SEQ ID NO:11 which is capable of binding an anti-Repantibody specific for a protein which may comprise an amino acidsequences as depicted in SEQ ID NO: 11; or (iii) an amino acid sequencehaving a 90% or more homology to the amino acid sequence of (i) or (ii)and is capable of binding an anti-Rep antibody specific for a proteinwhich may comprise an amino acid sequences as depicted in SEQ ID NO: 11.

In other embodiments the Rep protein is encoded by the CMI3 genome andmay comprise (i) an amino acid sequence as depicted in SEQ ID NO:12;(ii) a fragment of SEQ ID NO:12 which is capable of binding an anti-Repantibody specific for a protein which may comprise an amino acidsequences as depicted in SEQ ID NO: 12; or (iii) an amino acid sequencehaving a 90% or more homology to the amino acid sequence of (i) or (ii)and is capable of binding an anti-Rep antibody specific for a proteinwhich may comprise an amino acid sequences as depicted in SEQ ID NO: 12.

In certain embodiments an increased amount of Rep protein in a samplefrom a subject as compared to a Rep protein amount in a control samplecorrelates with a diagnosis of a neurodegenerative disease, e.g. MS,i.e. indicates MS. According to the present invention diagnosis of aneurodegenerative disease, e.g. MS or a predisposition for theneurodegenerative disease, e.g. MS, is indicated by an increased amountof Rep protein of at least 2 fold as compared to a control sample.

In other embodiments an increased amount of anti-Rep antibodies in asample from a subject as compared to anti-Rep antibody amount in acontrol sample correlates with a diagnosis of a neurodegenerativedisease, e.g. MS, i.e. is indicative for MS. According to the presentinvention diagnosis of a neurodegenerative disease, e.g. MS or apredisposition for a neurodegenerative disease, e.g. MS is indicated byan increased amount of anti-Rep antibodies of at least 2 fold ascompared to a control sample.

The Rep protein of the present invention may be employed in virtuallyany assay format that employs a known antigen to detect antibodies orcell-mediated immune responses. Thus, the present invention alsoencompasses the detection of cell-mediated, e.g. T-cell immune responsesagainst Rep protein.

In certain embodiments the invention provides a method of diagnosing aneurodegenerative disease in a subject which may comprise the steps ofincubating a sample from a subject with a Rep protein; detecting theamount of antibodies in the sample from the subject forming animmunological complex with Rep protein; and correlating the amount ofantibody bound to Rep protein, as compared to an amount in a controlsample, with a diagnosis of a neurodegenerative disease.

In particular embodiments the invention provides a method of diagnosingMS in a subject which may comprise the steps of incubating a sample froma subject with a Rep protein; detecting the amount of antibodies in thesample from the subject forming an immunological complex with Repprotein; and correlating the amount of antibody bound to Rep protein, ascompared to an amount in a control sample, with a diagnosis of MS.

In particular embodiments the Rep protein is immobilized, e.g. attachedto a support or carrier, followed by incubating the immobilized Repprotein with the sample from the subject.

In other embodiments the Rep protein is expressed in cells followed byincubating the cells with the sample from the subject.

In certain embodiments the amount of antibodies forming an immunologicalcomplex with Rep protein is quantified by an additional binding agentcoupled to a signal generating compound which is capable of binding tothe anti-Rep antibodies of the immunological complex, for example adetectably labeled secondary antibody, preferably anti-human antibody.

In other embodiments the antibodies in the sample from the subject areimmobilized followed by incubating with a defined amount of Rep protein.

Preferably, the sample from the subject and the control sample is ablood sample such as a serum or a plasma sample.

In other embodiments the invention provides a method of diagnosing aneurodegenerative disease in a patient which may comprise the steps ofdetecting the amount of Rep protein in a sample from a subject byanti-Rep antibodies, and correlating the amount of Rep protein detectedin the sample from a subject in step (a) as compared to an amount in acontrol sample with a diagnosis of a neurodegenerative disease.

In certain embodiments the invention provides a method of diagnosing MSin a patient which may comprise the steps of detecting the amount of Repprotein in a sample from a subject by anti-Rep antibodies, andcorrelating the amount of Rep protein detected in the sample from asubject in step (a) as compared to an amount in a control sample with adiagnosis of MS.

In such embodiments the sample from a subject and the control sample areselected from the group consisting of a serum sample, plasma sample ortissue sample.

In particular embodiments the anti-Rep antibody binds to an epitope thatis within an amino acid sequence selected from the group consisting ofamino acids from 1 to 136, from 137 to 229 and from 230 to 324 of SEQ IDNO:1. For example, the antibody binds to an epitope which may compriseSEQ ID NO:2 or SEQ ID NO:3.

In further embodiments the invention provides a kit for use in thediagnosis of MS which may comprise (a) a Rep protein, in particular aMSBI1, a MSBI2, CMI1, CMI2 or CMI3 Rep protein, (b) an additionalbinding agent coupled to a signal generating compound, for example, ananti-human antibody coupled to a detectable label and capable of bindingto anti-Rep antibody according to the invention, and (c) a solid matrixsuitable for immobilizing a Rep protein according to (a) or anti-Repantibodies, wherein aid antibodies are suspected in a sample, inparticular a serum or a plasma sample.

In particular embodiments the kit is put together for use in animmunoassay, for example selected from the group consisting ofenzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA),enzyme immune assay (EIA), fluorescence immunoassay (FIA), luminescenceimmunoassay (LIA) and strip assay.

Accordingly, it is an object of the invention not to encompass withinthe invention any previously known product, process of making theproduct, or method of using the product such that Applicants reserve theright and hereby disclose a disclaimer of any previously known product,process, or method. It is further noted that the invention does notintend to encompass within the scope of the invention any product,process, or making of the product or method of using the product, whichdoes not meet the written description and enablement requirements of theUSPTO (35 U.S.C. § 112, first paragraph) or the EPO (Article 83 of theEPC), such that Applicants reserve the right and hereby disclose adisclaimer of any previously described product, process of making theproduct, or method of using the product. It may be advantageous in thepractice of the invention to be in compliance with Art. 53(c) EPC andRule 28(b) and (c) EPC. All rights to explicitly disclaim anyembodiments that are the subject of any granted patent(s) of applicantin the lineage of this application or in any other lineage or in anyprior filed application of any third party is explicitly reserved.Nothing herein is to be construed as a promise.

It is noted that in this disclosure and particularly in the claimsand/or paragraphs, terms such as “comprises”, “comprised”, “comprising”and the like can have the meaning attributed to it in U.S. Patent law;e.g., they can mean “includes”, “included”, “including”, and the like;and that terms such as “consisting essentially of” and “consistsessentially of” have the meaning ascribed to them in U.S. Patent law,e.g., they allow for elements not explicitly recited, but excludeelements that are found in the prior art or that affect a basic or novelcharacteristic of the invention.

These and other embodiments are disclosed or are obvious from andencompassed by, the following Detailed Description.

DEPOSITS

The Deposits with Deutsche Sammlung für Mikroorganismen and Zellkulturen(DSMZ) [German Collection of Microorganisms and Cell Cultures], underdeposit accession numbers DSM ACC3327, DSM ACC3328, DSM ACC3329, ACC3330and antibody MSBI1 961-2-2 were made pursuant to the terms of theBudapest Treaty. Upon issuance of a patent, all restrictions upon thedeposit will be removed, and the deposit is intended to meet therequirements of 37 CFR §§ 1.801-1.809. The deposit will be irrevocablyand without restriction or condition released to the public upon theissuance of a patent and for the enforceable life of the patent. Thedeposit will be maintained in the depository for a period of 30 years,or 5 years after the last request, or for the effective life of thepatent, whichever is longer, and will be replaced if necessary duringthat period.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example, but notintended to limit the invention solely to the specific embodimentsdescribed, may best be understood in conjunction with the accompanyingdrawings.

FIG. 1 shows an example serum screening of 2×8 samples by serumincubation of 1D-size-resolved Rep protein membrane stripes.Nitrocellulose stripes containing Rep protein were incubated with eachtwo different serum/plasma dilutions (1:500 and 1:2000) of the MS serumsample pool or the healthy donor plasma pool. Rep-bound human IgGs weredetected with anti-human IgG HRP-coupled secondary antibodies. Antibodysignals at the size of the full-length Rep protein target (see Coomassieprotein staining and anti-Rep WB controls on the right) were quantifiedby densitometry.

FIG. 2 shows a quantification of Rep-specific sero-responses based onELISA screening. 50, 100, 200, 400, or 800 ng Rep protein (targetantigen) were spotted per 96-well. After blocking and washing the Repprotein antigen was incubated with either a pooled MS serum sample or apooled control plasma sample at a dilution of 1:500 for 6 h at roomtemperature (RT). After washing and incubation with a HRP-coupledanti-human IgG HRP secondary antibody and a last washing step, thepresence of Rep-bound human IgGs was quantified by TMB substratereaction and absorbation measurement at 450 nm. Quantification reveals agood correlation of signal intensity and amount of Rep protein(antigen). On average, signal intensity levels of the MS pool exceedintensities of the control pool by at least a factor of 1.9. In general,ELISA based serum screening revealed detectable serum antibodies for atleast a serum dilution of 1:1000 (data not shown), so that the titer forthis experiment is likely to be greater 1:1000 in the region of1:2000-1:4000 or even greater after platform optimization.

FIG. 3 shows a quantification of Rep-specific sero-responses based onELISA screening. 200 ng Rep protein (target antigen) were spotted per96-well. After blocking and washing the Rep protein antigen wasincubated with either 7 individual MS sera or 7 individual control serain duplicates at a dilution of 1:500 for 6 h at room temperature (RT).After washing and incubation with a HRP-coupled anti-human IgG HRPsecondary antibody and a last washing step, the presence of Rep-boundhuman IgGs was quantified by TMB substrate reaction and absorptionmeasurement at 450 nm. Average intensities of the MS samples exceed theaverage intensity of the control sera by at least a factor of 8 withsome MS samples revealing a factor of 10-16 over the average controlintensities.

FIGS. 4 to 6 show immunofluorescence image data obtained by employmentof anti-Rep antibodies A, B, C, D1 and D2 which are designated on they-coordinates.

FIG. 7 shows a Western Blot Analysis, wherein A, B, C and D1 designatethe groups of the employed anti-Rep antibodies.

FIG. 8 shows a sequence alignment of “optimized” (=SEQ ID NO:13) vs.“original” (=the wild-type; SEQ ID NO:15) MSBI1 sequence. The optimizedcodons are marked.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides diagnostic screening assays for the presence ofanti-Rep antibodies as pathogenic markers. Samples containing increasedamounts of anti-Rep antibodies indicate that the corresponding subjectwas definitely exposed to Rep-related protein or himself expressed Repprotein during a time period long enough to induce a Rep proteinspecific immune response. With such screening assays a diagnosis,prognosis and monitoring of MS based on the quantification of anti-Repantibodies can be conducted. In alternative embodiments Rep protein maybe directly detected and quantified in samples by anti-Rep antibodies.

“Rep protein” as used herein refers to a DNA-replication-associatedprotein (RepB). The Rep protein may comprise DNA binding activity andcould be essential for initiation of replication of episomal/viral DNAmolecules. In general Rep protein refers to a Rep protein from the groupof the Small Sphinx Genome (Whitley et al., 2014). In particular, theRep protein is a MSBI1 genome-encoded Rep protein (MSBI1 Rep), a MSBI2genome-encoded Rep protein (MSBI2 Rep), a CMI1 genome-encoded Repprotein (CMI1 Rep), a CMI2 genome-encoded Rep protein (CMI2 Rep) or CMI3genome-encoded Rep protein (CMI3 Rep). Preferably, the MSBI1 Rep proteinis encoded by MSBI1.176 deposited in the EMBL databank under the acc.no. LK931491 and has the amino acid sequence as depicted in SEQ ID NO:1or the Rep protein is MSBI2 encoded by MSBI2.176 deposited in the EMBLdatabank under the acc. no. LK931492 and has the amino acid sequence asdepicted in SEQ ID NO:8 (Whitley, Gunst et al. 2014). In anotherpreferred embodiment the CMI1 Rep protein is encoded by CMI1.252deposited in the EMBL databank under the acc. no. LK931487 and has theamino acid sequence as depicted in SEQ ID NO:10. In another preferredembodiment the CMI2 Rep protein is encoded by CMI2.214 deposited in theEMBL databank under the acc. no. LK931488 and has the amino acidsequence as depicted in SEQ ID NO:11. In another preferred embodimentthe CMI3 Rep protein is encoded by CMI3.168 deposited in the EMBLdatabank under the acc. no. LK931489 and has the amino acid sequence asdepicted in SEQ ID NO:12. In a particular preferred embodiment the Repprotein may comprise a N-terminal region conserved among small Sphinxgenomes consisting essentially of amino acids from 1 to 229 of SEQ IDNO:1 and a C-terminal variable region specific for MSBI1.176 consistingessentially from amino acids 230 to 324 of SEQ ID NO:1. The N-terminalconserved region may comprise a putative, first DNA binding domainconsisting essentially of amino acids from 1 to 136 of SEQ ID NO: 1 anda second putative DNA binding domain consisting essentially of aminoacids from 137 to 229 of SEQ ID NO:1.

“Rep protein” also encompasses fragments and variants of the proteinwith SEQ ID NO:1 or SEQ ID NO:8 which are capable of binding an anti-Repantibody specific for Rep protein having the amino acid sequence of SEQID NO:1 or SEQ ID NO:8. Preferably, such a fragment is an immunogenicfragment of the protein having the amino acid sequence of SEQ ID NO:1 orSEQ ID NO:8 which encompasses at least one epitope for an anti-Repprotein antibody against the Rep protein of SEQ ID NO:1 or SEQ ID NO:8and, preferably, may comprise at least 7, 8, 9, 10, 20, 25 or 50contiguous amino acids. In particular embodiments the fragment maycomprise or consists essentially of a domain of the Rep protein, forexample, the N-terminal conserved region, the C-terminal variableregion, the first or second DNA binding domain. A variant of the proteinwith SEQ ID NO:1 or SEQ ID NO:8 may comprise one or more amino aciddeletions, substitutions or additions compared to SEQ ID NO:1 and has ahomology of at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%to the amino acid sequence of SEQ ID NO:1 or SEQ ID NO:8, wherein thevariant is capable of binding an anti-Rep antibody specific for a Repprotein having the amino acid sequence of SEQ ID NO:1 or SEQ ID NO:8.Included within the definition of variant are, for example, polypeptidescontaining one or more analogues of an amino acid (including, forexample, unnatural amino acids, peptide nucleic acid (PNA), etc.),polypeptides with substituted linkages, as well as other modificationsknown in the art, both naturally occurring and non-naturally occurring.The term Rep protein includes fusion proteins with a heterologous aminoacid sequence, with a leader sequence or with a Tag-sequence and thelike. In certain embodiments of the invention protein tags aregenetically grafted onto the Rep protein described above, for examplethe Rep protein selected from the group consisting of MSBI1, MSBI2,CMI1, CMI2 or CMI3. In particular at least one protein tag is attachedto a polypeptide consisting of an amino acid sequence as depicted in anyone of SEQ ID NOs:1-3,8-12,14. Such protein tags may be removable bychemical agents or by enzymatic means. Examples of protein tags areaffinity or chromatography tags for purification. For example the Repprotein may be fused to a Tag-sequence, for example, selected from thegroup consisting of His6-Tag (SEQ ID NO:4), T7-Tag (SEQ ID NO:5),FLAG-Tag (SEQ ID NO:6) and Strep-Il-Tag (SEQ ID NO:7). a His-Tag (SEQ IDNo:4), a T7-Tag (SEQ ID NO:5), FLAG-Tag (SEQ ID NO:6) or StrepII-Tag(SEQ ID NO:7). Further, fluorescence tags such as green fluorescenceprotein (GFP) or its variants may be attached to a Rep-protein accordingto the invention.

In a particular preferred embodiment the MSBI1 genome-encoded Repprotein (MSBI1 Rep) is codon-optimized for the production in human celllines (e.g. HEK-293, HEK293TT, HEK293T, HEK293FT, HaCaT, HeLa, SiHa,CaSki, HDMEC, L1236, L428, BJAB, MCF7, Colo678, any primary cell lines)as well as bovine (e.g. MAC-T) or murine cell lines (e.g. GT1-7). Asregards codon optimization, the nucleotide sequences that encode theantigens can be designed to employ codons that are used in the genes ofthe subject in which the antigen is to be produced. In a preferredembodiment, the codons used are “humanized” codons. Such codon usageprovides for efficient expression of the antigens in human cells. Anysuitable method of codon optimization may be used. Such methods and theselection of such methods are well known to those of skill in the art.According to the present invention, such a codon-optimized variant ofthe MSBI1 genome-encoded Rep protein (MSBI1 Rep) may comprise or has thesequence as depicted in SEQ ID. No.: 13 and may comprise or has theamino acid sequence as depicted in SEQ ID. No.: 14. In total, a numberof 686 nucleotides of the 927 nucleotide MSBI1 Rep gene encoding for theRep protein (from start to stop codon) were substituted to improve codonusage. A perfect codon usage with optimal adaptation towards e.g. thehuman codon usage is described by a codon adaptation index (CAI) of 1indicating that all codons are optimized for human expression. For theoriginal MSBI1-encoded Rep gene, a CAI of 0.67 for the human system wascalculated, which is far below the a CAI of 0.8, which is considered asthe lower threshold for good codon adaptation. After codon optimizationof the MSBI1 rep gene, a CAI of 0.94 was calculated for the optimizedDNA indicating an almost optimal codon adaptation for the human system.Especially, a number of 18 very rarely used codons were modified, mostof them representing codons coding for leucine with a very low usagefrequency (<10%) in the human system. A sequence alignment of thecodon-optimized MSBI1 sequence of SEQ ID NO:13 vs. the wild-type MSBI1sequence of SEQ ID NO:15 is shown in FIG. 8 .

The Rep protein of the invention, including the Rep fragments and Repvariants as defined above, can be prepared by classical chemicalsynthesis. The synthesis can be carried out in homogeneous solution orin solid phase. The polypeptides according to this invention can also beprepared by means of recombinant DNA techniques. An example forproducing and purification of a Rep protein according to the inventionis shown in Example 1.

“Subject” as used herein refers to a mammalian individual or patient,including murines, cattle, for example bovines, simians and humans.Preferably, the subject is a human patient.

“Sample” as used herein refers to a biological sample encompassingliquid and solid samples. Liquid samples encompass blood liquids suchas, for example, sera, plasma and cerebrospinal fluid (CSF). Solidsamples encompass tissue samples such as tissue cultures or biopsyspecimen.

“Correlates with” as used herein refers to an amount, i.e. level ortiter, of anti-Rep antibodies and Rep protein, respectively, with asignificant correlation with a disease status of, for example, MS. Thecorrelation is determined by detecting the extent of difference in theamount present in a sample from a subject to be tested and a controlsample. “Control sample” means a single sample or an average of various,i.e. more than two, control samples. The control is taken from a healthyindividual who has not been diagnosed for MS. Alternatively, thecorrelation may be theoretically determined by detecting the extent ofdifference in the amount present in a sample for a subject to be testedwith a predetermined cut-off value. A cut-off value is a reference valuewith statistically significant separation between different diseasestatus, e.g. between healthy and diseased status. The cut-off value canbe determined by statistical analysis of a sufficiently large panel oftest samples from patients with disease history and samples from healthytest group by statistical tests known in the art.

In certain embodiments a diagnosis, for example of MS, is indicated byan at least 2 fold, 3 fold, 4 fold, 5 fold, 10 fold, 50 fold, 100 fold,500 fold or 1000 fold increased amount of protein, i.e. Rep protein andanti-Rep-antibodies, respectively, in the sample from the subject ascompared to a control sample.

“Anti-Rep antibody” as used herein refers to an antibody binding at adetectable level to Rep protein in the methods of the invention whichaffinity is more strongly to the Rep protein of the invention than to anon-Rep protein. Preferably, the antigen affinity for Rep protein is atleast 2 fold larger than background binding. In particular the anti-Repantibody is specific for the MSBI1 Rep having the amino acid sequence ofSEQ ID NO:1 or MSBI2 Rep. In particular embodiments the antibody iscross-specific for MSBI1 Rep, MSBI2 Rep, CMI1 Rep, CMI2 Rep and/or CMI3Rep. In certain embodiments the anti-Rep antibody is cross-specific forfor at least two, preferably all, off MSBI1 Rep, MSBI2 Rep, CMI1 Rep,CMI2 Rep and/or CMI3 Rep and binds to an epitope within amino acids from1 to 136 of SEQ ID NO: 1.

A common feature of all assays is that the Rep protein is contacted witha sample suspected of containing anti-Rep protein antibodies underconditions that permit the Rep protein to bind to any such antibodypresent in the sample. Such conditions will typically be physiologictemperature, pH and ionic strength using an excess of Rep protein. Theincubation of the Rep protein with the sample is followed by detectionof immune complexes comprised of the antigen. In certain embodimentseither the Rep protein is coupled to a signal generating compound, e.g.detectable label, or an additional binding agent, e.g. secondaryanti-human antibody, coupled to a signal generating compound is used fordetecting the immune complex.

Anti-Rep antibodies can be detected and quantified in assays based onRep protein as protein antigen, which serves as target for themammalian, e.g. human, antibodies suspected in the sample. Preferably,the Rep protein is purified (e.g. see Example 1) and the samples can be,for example, serum or plasma samples. The methods include immobilizationof Rep protein on a matrix followed by incubation of the immobilized Repprotein with the samples. Finally, the Rep-bound antibodies of theformed immunological complex between Rep protein and antibodies of thesamples are quantified by a detection binding agent coupled to a signalgenerating compound, e.g. secondary HRP-(horseradish-peroxidase)-coupleddetection antibody allowing for HRP-substrate based quantification. Thissignal generating compound or label is in itself detectable or may bereacted with an additional compound to generate a detectable product.

In other embodiments anti-Rep antibodies are indirectly quantified inthat first the antibodies of the sample are immobilized on a matrix,followed by incubation with a defined amount of Rep protein which may belabelled or comprise a Tag protein, wherein the anti-Rep antibodiesimmobilized and present on the matrix capture the Rep protein from theprotein-sample liquid mixture, followed by quantification of the boundRep protein.

In other embodiments Rep protein can be expressed in cells and thesecells are incubated with the sample. Thereafter, anti-Rep antibodiesfrom the sample bound to the Rep protein expressed by cells are detectedand quantified.

Design of the immunoassay is subject to a great deal of variation, andmany formats are known in the art. Protocols may, for example, use solidsupports, or immunoprecipitation. Most assays involve the use of bindingagents coupled to signal generating compounds, for example labelledantibody or labelled Rep protein; the labels may be, for example,enzymatic, fluorescent, chemiluminescent, radioactive, or dye molecules.Assays which amplify the signals from the immune complex are also known;examples of which are assays which utilize biotin and avidin orstreptavidin, and enzyme-labeled and mediated immunoassays, such asELISA assays.

The immunoassay may be in a heterogeneous or in a homogeneous format,and of a standard or competitive type. In a heterogeneous format, thepolypeptide (Rep protein or anti-Rep antibody) is typically bound to asolid matrix or support or carrier to facilitate separation of thesample from the polypeptide after incubation. Examples of solid supportsthat can be used are nitrocellulose (e.g., in membrane or microtiterwell form), polyvinyl chloride (e.g., in sheets or microtiter wells),polystyrene latex (e.g., in beads or microtiter plates, polyvinylidinefluoride (known as Immunolon), diazotized paper, nylon membranes,activated beads, and Protein A beads. The solid support containing theantigenic polypeptides is typically washed after separating it from thetest sample, and prior to detection of bound anti-Rep antibodies. Bothstandard and competitive formats are known in the art.

In a homogeneous format, the test sample is incubated with the Repprotein in solution. For example, it may be under conditions that willprecipitate any Rep protein-antibody complexes which are formed. Bothstandard and competitive formats for these assays are known in the art.

In a standard format, the amount of anti-Rep antibodies in theantibody-Rep protein complexes is directly monitored. This may beaccomplished by determining whether (labelled) anti-xenogeneic (e.g.anti-human) antibodies which recognize an epitope on anti-Rep antibodieswill bind due to complex formation. In a competitive format, the amountof anti-Rep antibodies in the sample is deduced by monitoring thecompetitive effect on the binding of a known amount of labelled antibody(or other competing ligand) in the complex.

Complexes formed which may comprise anti-Rep antibody (or in the case ofcompetitive assays, the amount of competing antibody) are detected byany of a number of known techniques, depending on the format. Forexample, unlabeled anti-Rep antibodies in the complex may be detectedusing a conjugate of anti-xenogeneic Ig complexed with a label (e.g. anenzyme label, such as, for example, HRP).

In an immunoprecipitation or agglutination assay format the reactionbetween the Rep protein and the anti-Rep antibody forms a network thatprecipitates from the solution or suspension and forms a visible layeror film of precipitate. If no anti-Rep antibody is present in thesample, no visible precipitate is formed.

The solid phase selected can include polymeric or glass beads,nitrocellulose, microparticles, microwells of a reaction tray, testtubes and magnetic beads. The signal generating compound can include anenzyme, a luminescent compound, a chromogen, a radioactive element and achemiluminescent compound. Examples of enzymes include alkalinephosphatase, horseradish peroxidase (HRP) and beta-galactosidase.Examples of enhancer compounds include biotin, anti-biotin and avidin.Examples of enhancer compounds binding members include biotin,anti-biotin and avidin.

In further embodiments the invention provides methods wherein anincreased amount of Rep protein in a sample correlates with a diagnosisor predisposition of a neurodegenerative disease, for example MS, or isused for monitoring the disease, for example MS, or monitoring thetreatment of the disease, for example MS. In such embodiments the Repprotein in the sample is detected by anti-Rep antibodies.

Such methods may comprise the steps of detecting the amount of Repprotein in a sample from a subject by anti-Rep antibodies; andcorrelating the amount of Rep protein detected in the sample from asubject in step (a) as compared to an amount in a control sample with adiagnosis of a neurodegenerative disease, for example MS.

Examples for assays which can be used in such methods for the detectionof Rep protein in serum or plasma samples include, but are not limitedto immunoprecipitation, immunofluoresence, dot blotting and WesternBlot.

For example, a serum sample may be incubated with anti-Rep proteinantibodies to capture the Rep protein in the sample, followed by a stepof immunoprecipitation of Rep protein and, thereafter, a step ofdetection by SDS-PAGE and Western Blot.

In a further example, a dot blot membrane may be incubated with serum,followed by the step of a SDS-PAGE and Western Blot.

In a further example, serum dilutions of the sample are loaded onSDS-Page followed by a Western Blot.

In further embodiments Rep protein is detected in tissue samples byimmunohistochemical methods or immunofluoresence microscopy.

In certain embodiments anti-Rep antibodies are used for the detection orcapturing of the Rep protein in the sample.

The term “antibody”, preferably, relates to antibodies which consistessentially of pooled polyclonal antibodies with different epitopicspecificities, as well as distinct monoclonal antibody preparations. Asused herein, the term “antibody” (Ab) or “monoclonal antibody” (Mab) ismeant to include intact immunoglobulin molecules as well as antibodyfragments (such as, for example, Fab and F(ab′)2 fragments) which arecapable of specifically binding to Rep protein. Fab and F(ab′)2fragments lack the Fc fragment of intact antibody, clear more rapidlyfrom the circulation, and may have less non-specific tissue binding thanan intact antibody. Thus, these fragments are preferred, as well as theproducts of a FAB or other immunoglobulin expression library. Moreover,antibodies useful for the purposes of the present invention includechimeric, single chain, multifunctional (e.g. bispecific) and humanizedantibodies or human antibodies.

In certain embodiments the antibody or antigen binding fragment thereofis coupled to a signal generating compound, e.g., carries a detectablelabel. The antibody or antigen binding fragment thereof can be directlyor indirectly detectably labeled, for example, with a radioisotope, afluorescent compound, a bioluminescent compound, a chemiluminescentcompound, a metal chelator or an enzyme. Those of ordinary skill in theart will know of other suitable labels for binding to the antibody, orwill be able to ascertain such, using routine experimentation.

Anti-Rep antibodies are, preferably, raised (generated) against a Repprotein having the amino acid sequence of SEQ ID NO:1 or SEQ ID NO:8 ora fragment thereof by methods well known to those skilled in the art.

In certain embodiments anti-Rep antibodies are used in the methods ofthe invention which are capable of binding to several or all kinds ofRep proteins from the group of the Small Sphinx Genome(anti-Small-Sphinx-like Rep antibody or anti-SSLRep antibody). Suchanti-SSLRep antibody binds to an epitope within the conserved N-terminalregion of the Rep protein from amino acids 1 to 229 of SEQ ID NO:1. Inparticular embodiments anti-Rep antibodies of the anti-SSLRep type areused which bind to an epitope within SEQ ID NO:2 (amino acids 32-49 ofSEQ ID NO:1) or SEQ ID NO:3 (amino acids 197-216 of SEQ ID NO:1). Thepeptide fragments of SEQ ID NO:2 and SEQ ID NO:3 are highly conservedamong the Rep proteins from the Small Sphinx Genome group and appear tobe exposed due to their hydrophilic character. Anti-Rep antibodies ofthe anti-SSLRep type may be produced by immunization, for example ofmice or guinea pig, by peptides consisting essentially of the amino acidsequences as depicted in SEQ ID NOs:2 or 3; or by other immunogenicfragments, preferably which may comprise at least 8-15 amino acids,derived from the conserved N-terminal Rep protein region from aminoacids 1 to 229 of SEQ ID NO:1.

In further embodiments anti-Rep antibodies specific for MSBI1 Repprotein are used. Such antibodies may be produced, for example, byimmunization of a mammal such as mice or guinea pig with a full-lengthRep protein having the amino acid sequence of SEQ ID NO:1.

Preferably, the methods of the invention use anti-Rep antibodies whichare capable of detecting Rep protein up to ranges from picogramm tofemtogramm in different kinds of body liquids such as, for example,blood, serum, spinal fluid or cerebral fluid.

In the methods of the invention either a specific kind of anti-Repantibody or a pool of two or more different kinds of anti-Rep antibodiesmay be used. If a pool of different kinds of anti-Rep antibodies isused, the anti-Rep antibody pool may comprise different anti-Repantibodies binding to different epitopes within different domains of theRep protein, e.g. first DNA binding domain (e.g. aa 1-136 of SEQ IDNO:1), second DNA binding domain (e.g. aa 137-229 of SEQ ID NO:2) and/orvariable domain (e.g. aa 230-324 of SEQ ID NO:1), in particular, ofMSBI1 Rep protein (SEQ ID NO:1).

In a further embodiment anti-Rep antibodies are used for screening ofprobes from patients and/or healthy individuals for a Rep protein. Theselective detection of a Rep protein in tissues of patients, e.g. of aneurodegenerative disease, is indicative for a causality between theisolated DNA genome of the Rep protein detected in the sample and thedisease of the patient from whom the sample was derived.

For the detection of a Rep protein by anti-Rep antibodies methods suchas, for example, Western Blot, immunofluoresence microscopy orimmunohistochemical methods may be applied.

In certain embodiments anti-Rep antibodies are used which are capable ofdetecting a Rep protein at certain celluar localisations. For instancethe anti-Rep antibody may detect the Rep protein in cytoplasm, nuclearmembrane and nucleus or detect speckles in cytoplasm. Examples of suchgroups of anti-Rep antibodies are shown in Table 1:

Antibody RepProtein DSMZ Group Localisation Specificity Antibody depositGroup A cytoplasm + MSBI1 + AB01 DSM nuclear small-sphinx- 523-1-1ACC3327 membrane like (+nucleus) Group B speckles in MSBI1 + AB02 DSMcytoplasm small-sphinx- 304-4-1 ACC3328 like Group C cytoplasm + MSBI1MSBI1 DSM nuclear specific 381-6-2 ACC3329 membrane (+nucleus) Group Dspeckles in MSBI1 D1: MSBI1 DSM cytoplasm specific 961-2-2 ACC3330 D2:MSBI1 761-5-1

Anti-Rep antibodies of group A have an epitope within the amino acidsequence depicted in SEQ ID NO:3 (aa 198-217 of SEQ ID NO:1) and arecapable of detecting MSBI1 Rep and Rep proteins which may comprise thisconserved epitope of the Small Sphinx Genome group (e.g. MSBI2, CMI1,CMI4). In immunofluoresence assays such anti-Rep antibodies detect aspecific Rep localisation pattern, wherein the main localisation ishomogeneously distributed over the cytoplasm and nuclear membrane; andadditional weak and homogeneously distributed localisation is seen inthe nucleus. An example of such a group A antibody is antibody AB01523-1-1 (DSM ACC3327) which was employed in the examples as group Aantibody.

Anti-Rep antibodies of group B have an epitope within the amino acidsequence depicted in SEQ ID NO:2 (aa 33-50 of SEQ ID NO:1) and arecapable of detecting MSBI1 Rep and Rep proteins which may comprise thisconserved epitope of the Small Sphinx Genome group (e.g. MSBI2, CMI1,CMI4). In immunofluoresence assays such anti-Rep antibodies detectspecifically speckles (cytoplasmatic aggregations) of the Rep protein(often in the periphery of the nuclear membrane). An example of such agroup B antibody is the antibody designated as AB02 304-4-1 (DSMACC3328) which was employed in the examples as group B antibody.

Anti-Rep antibodies of group C detect specifically a structural epitopeof MSBI1 (SEQ ID NO:1). In immunofluoresence assays such anti-Repantibodies detect a specific Rep localisation pattern, wherein the mainlocalisation is homogeneously distributed over the cytoplasm and nuclearmembrane; and additional weak and homogeneously distributed localisationis seen in the nucleus. An example of such a group C antibody isantibody MSBI1 381-6-2 (DSM ACC3329) which was employed in the examplesas group C antibody.

Anti-Rep antibodies of group D detect specifically a structural epitopeof MSBI1 (SEQ ID NO:1), where antibody MSBI1 961-2-2 designated as “D1”detects an epitope depicted in SEQ ID NO:9 (aa 281-287) in theC-terminal domain of MSBI1. Antibody MSBI1 761-5-1 (DSM ACC3328)designated as “D2” detects a 3D structural epitope of MSBI1 which isexclusively accessible under in vivo conditions and is not accessible inWestern Blots. In immunofluoresence assays such anti-Rep antibodiesdetect specifically speckles (cytoplasmatic aggregations) of the Repprotein (often in the periphery of the nuclear membrane.

In certain embodiments the anti-Rep antibodies of groups A, B, C or D;or a combination of anti-Rep antibodies of at least two different groupsA, B, C or D are used to determine the kind of Rep protein localisationin a probe and if such a Rep protein localisation correlates with apathogen function. For instance, if speckles are present. In certainembodiments, i.e., methods or kits of the invention, at least oneanti-Rep antibody selected from groups A and B is combined with at leastone anti-Rep antibody selected from groups C and D. In particularembodiments, i.e., methods or kits of the invention, an anti-Repantibody of group A is combined with at least one further anti-Repantibody selected from the groups B, C, and D. For instance, an anti-Repantibody of group A may be combined with further anti-Rep antibodies ofgroups C and D. Such combinations of anti-Rep antibodies of differentgroups increases the distinctness of the diagnostic assessment, inparticular for the diagnosis of MS. These groups A, B, C or D antibodiesare preferred for use in the diagnosis of MS.

The following antibodies were deposited with the Deutsche Sammlung fürMikroorganismen and Zellkulturen (DSMZ) [German Collection ofMicroorganisms and Cell Cultures] on Sep. 28, 2017:

-   -   antibody AB01 523-1-1 under DSM ACC3327;    -   antibody AB02 304-4-1 under DSM ACC3328;    -   antibody MSBI1 381-6-2 under DSM ACC3329; and    -   antibody MSBI1 761-5-1 under DSM ACC3330.    -   Antibody MSBI1 961-2-2 has been deposited with DSMZ on Oct. 6,        2017.

In further embodiments a kit for use in the diagnosis of MS is provided.The kit may include material for detecting anti-Rep antibodies and/orRep protein together with instructions for use of the materials inassays for the diagnosis of MS. The kit may comprise one or more of thefollowing components: a biomarker according to the invention, i.e. Repprotein and anti-Rep antibodies, e.g. antibodies of Table 1,respectively; a signal generating compound, a solid matrix for attachinga capturing agent, a diluent for the samples, a wash buffer. Signalgenerating compound refers to a detectable label which is either coupledto an additional binding agent capable of binding to the biomarker ofthe invention or directly coupled with the biomarker of the invention.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined in the appended claims.

The present invention will be further illustrated in the followingExamples which are given for illustration purposes only and are notintended to limit the invention in any way.

EXAMPLES Example 1: MSB11 Rep Protein Purification

A nucleotide acid molecule encoding full-length Rep open reading frame(ORF) identified within the MSBI1 genome is cloned into an expressionplasmid (pEXP5-CT, Invitrogen) enabling protein expression based on anE. coli high yield cell free in vitro translation system (Expressway™Cell-Free E. coli Expression System, Invitrogen). The synthesized Repprotein having the amino acid sequence of SEQ ID NO:1 within the invitro translation reaction is denaturated by adding 20 reaction volumes8 M urea sample buffer pH 8.0 containing 100 mM NaH2PO4, 10 mM Tris HCl,pH 8.0, 5 mM imidazole. The Rep protein is subsequently purified underdenaturating conditions (20 mM imidazole for washing and 300 mMimidazole for protein elution) based on a C-terminal His6-tag fused tothe Rep protein. Quality of purification is determined by Coomassieprotein staining and Western Blotting with anti-Rep protein antibodies.The Rep protein purity is densitometrically calculated and greater 95%.The purified protein is either directly used for ELISA-based serumscreening or subjected to SDS-Page followed by transfer blotting ontonitrocellulose membranes for serum incubation of 1D-size-resolved Repprotein membrane stripes.

Example 2: Generation of Serum Master Plates

Serum samples are first aliquoted to reduce sample freeze-thaw cycles.Then, a master plate is established by generating a 1:1 dilution ofserum in PBS pH 7.2 stabilized by 0.02% (w/v) sodium azide finalconcentration in U-shape 96-well plate. This plate is stable for atleast 2 months when stored at 4° C. and handled under sterile conditionsand is used as template for further serum dilution (1:20 final dilution)prior to the individual screening experiment.

Example 3: Serum Screening by Serum Incubation of 1D-Size-Resolved RepProtein Membrane Stripes

For screening assays based on incubation of 1D-resolved Rep proteinmembrane stripes with serum, 20 μg purified Rep protein is loaded ontoSigma Tru-PAGE 4-20% precast gels. The walls separating the gel pocketsare removed before gel loading to produce one large pocket and a singlepocket for a size marker. After the 1D-size resolved SDS-PAGE, theprotein is transfer-blotted onto nitrocellulose membranes using astandard wet/tank transfer blot protocol. After that, the protein on theblot membrane (essentially one band of full-length Rep protein at around40 kDa running height) is visualized with PonceauS to check transferquality and to prepare the cutting of membrane stripes of 2 mm width andthe height of the full 1D-size-resolved membrane. The stripes are thenblocked 1 h with each 500 μlserum-free blocking reagent (Genetex Tridentuniversal blocking reagent). After that, serum is characterized based ontwo different serum dilutions. Serum incubation is performed for 14 h(overnight) at 4° C. on a linear shaking device. After that, themembrane stripes are washed with PBS-T pH7.2 0.1% polysorbate (Tween®)20 for 3×5 min at room temperature. Detection of Rep-specific boundhuman IgGs within the sera is done by incubation with an HRP-coupledgoat anti-human IgG (H+L) secondary antibody for 1 h at roomtemperature. After three washes with PBS-T pH7.2 0.1% polysorbate(Tween®) 20 for 3×5 min at room temperature, the stripes of eachindividual serum incubation are fixed with tape on a plastic foil. Thefoil is then incubated with ECL substrate (Biorad Clarity) to visualizebound human IgGs on a BioRad WesternBlot detection system. Signalscorresponding to the amount of IgGs that specifically bind to the Repband on the protein membrane are quantified by densitometry.

An example for a result of 1D-size-resolved Rep protein membrane stripesis shown in FIG. 1 and the quantification of seropositive serum/plasmasamples is shown in Table 2: Almost 50% of the serum samples gave verystrong signals for both dilutions (1:500 and 1:2000) and only 3 of 21were totally negative. Of the plasma controls, 7 samples gaveintermediate signals at 1:500 dilution (some additional one with verylow signals) while at 1:2000 dilution only 3 samples gave a very weaksignal, while all the others were seronegative. All quantificationssustain the tendency that MS-serum intensities show at least a 30-foldexcess of signal when compared to control plasma intensities.

TABLE 2 Quantification of seropositive serum/plasma samples. serumdilution number of seropositive samples 1:2000 17 3 1:500  21 8 MS seracontrol plasma

Sera/plasma with detection of Rep-specific human IgGs were countedaccording to signal intensity for the serum/plasma dilution of 1:500 and1:2000 for the MS serum pool and the healthy control plasma pool (each21 in total). Almost 50% of the serum samples gave very strong signalsfor both dilutions (1:500 and 1:2000) and only 3 of 21 were totallynegative. Of the plasma controls, 7 samples gave intermediate signals at1:500 dilution (some additional one with very low signals) while at1:2000 dilution only 3 samples gave a very weak signal, while all theothers were seronegative. All quantifications sustain the tendency thatMS-serum intensities show at least a excess of signal when compared tocontrol plasma intensities.

Example 4: Serum Screening by ELISA

An appropriate amount of purified Rep protein (usually between 50 and200 ng per well) is added to a 1:1 mixture of 8 M urea pH 8.0 and PBS pH7.2 predisposed into a Maxisorp 96-well ELISA plate (Fisher Scientific).The protein is allowed to bind to the plate matrix for 14 h at 4° C. ona linear shaking device. Then the plate is washed with PBS-T pH 7.2 0.1%polysorbate (Tween®) 20 for 3×5 min at room temperature followed byblocking for at least 14 h at 4° C. with PBS pH 7.2 1% (w/v) BSA finallycontaining 0.02% sodium azide. After that the serum is added at adilution of 1:500 and incubation is performed for 6 h at roomtemperature. After that, the plate is washed with PBS-T pH 7.2 0.1%polysorbate (Tween®) 20 for 3×5 min at room temperature. Detection ofRep-specific bound human IgGs within the sera is done by incubation withan HRP-coupled goat anti-human IgG (H+L) secondary antibody for 1 h atroom temperature. After three washes with PBS-T pH 7.2 0.1% polysorbate(Tween®) 20 for 3×5 min at room temperature, 100 μl TMB(3,3′,5,5′-tetramethylbenzidine, HRP-sensitive) substrate solution isadded per well and incubated for 5 min at room temperature. The reactionis stopped by addition of 100 μl 8 M acetic acid/1M sulfuric acid.Signal intensity is quantified on a Perkin Elmer ELISA compatible deviceby measuring absorbance at 450 nm.

The result of an example of a quantification of Rep-specificsero-responses based on ELISA screening is shown in FIG. 2 :Quantification reveals a good correlation of signal intensity and amountof Rep protein (antigen). On average, signal intensity levels of the MSpool exceed intensities of the control pool by at least a factor of 1.9.In general, ELISA based serum screening revealed detectable serumantibodies for at least a serum dilution of 1:1000 (data not shown), sothat the titer for this experiment is likely to be greater 1:1000 in theregion of 1:2000-1:4000 or even greater after platform optimization.

Example 5: Immunofluorescence Analysis

HEK293TT cells (125.000/well) were cultured for 24 h inimmunofluorescence 8-well chambers in DMEM 10% FCS (supplemented with 1×Glutamax (Gibco) and 1× non-essential amino acids (Gibco)) followed byDNA transfection with polyethylenimine (PEI) of either the controlplasmid ZsGreen1CI (Clontech) expressing the auto-fluorescence markerprotein ZsGreen or the same plasmid bearing the full length MSBI1 RepORF at the 3-prime end coding for a ZsGreen-Rep fusion protein. 48 hoursafter DNA transfection, cells were washed with PBS, fixed for 20 min atRT with PBS 4% PFA at RT and permeabilized with PBS 0.5% Triton X-100for 10 min at RT on a shaking device. Cells were washed with PBS andblocking was performed with PBS 1% BSA for 45 min at RT. Incubation withthe mouse monoclonal anti-Rep antibodies (c.f. Table 1) was performedfor 1 h at 37° C. in PBS 1% BSA with 1:500 antibody dilutions (controlslacking primary antibodies were included). Cells were washed three timeswith PBS followed by incubation with PBS 1% BSA for 15 min at RT. Then,incubation with the secondary antibody (AlexaFluor546 goat anti-mouse,1:500; DNA marker Hoechst 33342, 1:5.000) was performed for 45 min at RTin PBS 1% BSA. Cells were washed three times with PBS 1% BSA and threetimes with PBS prior to mounting with cover slips (Dako mountingmedium). Immunofluorescence images were taken on a Zeiss Cell Observer(20× objective, fixed exposure time for sample and control dublets).

The immunofluorescence images (FIG. 4 ) show that antibody treatmentwith group A and C antibodies leads to specific detection ofcytoplam+nuclear membrane (+nucleus)-localized target protein withoutdetection of aggregates. In contrast, group B and D antibodies showspecific colocalization with speckled protein and no to weak levels ofcytoplasmatic signals. The control incubation of the antibodies on theZsGreen fusion protein alone did not result in significant signaldetection (same exposition times used for visualization of the antibodysignals).

Example 6: Immunofluorescence Analysis

HEK293TT cells (125.000/well) were cultured for 24 h inimmunofluorescence 8-well chambers in DMEM 10% FCS (supplemented with 1×Glutamax (Gibco) and 1× non-essential amino acids (Gibco)) followed byDNA transfection with polyethylenimine (PEI) of either the controlplasmid ZsGreen1CI (Clontech) expressing the auto-fluorescence markerprotein ZsGreen or the same plasmid bearing the full length CMI1 Rep ORFat the 3-prime end coding for a ZsGreen-Rep fusion protein. 48 hoursafter DNA transfection, cells were washed with PBS, fixed for 20 min atRT with PBS 4% PFA at RT and permeabilized with PBS 0.5% Triton X-100for 10 min at RT on a shaking device. Cells were washed with PBS andblocking was performed with PBS 1% BSA for 45 min at RT. Incubation withthe mouse monoclonal anti-Rep antibodies (Table 1) was performed for 1 hat 37° C. in PBS 1% BSA with 1:500 antibody dilutions (controls lackingprimary antibodies were included). Cells were washed three times withPBS followed by incubation with PBS 1% BSA for 15 min at RT. Then,incubation with the secondary antibody (AlexaFluor546 goat anti-mouse,1:500; DNA marker Hoechst 33342, 1:5.000) was performed for min at RT inPBS 1% BSA. Cells were washed three times with PBS 1% BSA and threetimes with PBS prior to mounting with cover slips (Dako mountingmedium). Immunofluorescence images were taken on a Zeiss Cell Observer(20× objective, fixed exposure time for sample and control dublets).

The immunofluorescence images (FIG. 5 ) show that while the group Aantibody specifically detects cytoplasm+nuclear membrane(+nucleus)-localized target protein without detection of aggregates,group B antibody detects speckled target protein with a minimalbackground of cytoplasmic localized target protein. The MSBI1-specificantibodies of group C and D do not lead to specific detection ofsignals. Both antibodies D1 and D2 belong to the “D” group but haveslightly different epitope recognition.

Example 7: Immunofluorescence Analysis

HEK293TT cells (125.000/well) were cultured for 24 h inimmunofluorescence 8-well chambers in DMEM 10% FCS (supplemented with 1×Glutamax (Gibco) and 1× non-essential amino acids (Gibco)) followed byDNA transfection with polyethylenimine (PEI) of either the controlplasmid pcDNA3.1(−) (Invitrogen) or the same plasmid expressing acodonoptimized variant of the full length MSBI1 Rep ORF (SEQ ID. No.:13). 48 hours after DNA transfection, cells were washed with PBS, fixedfor 20 min at RT with PBS 4% PFA at RT and permeabilized with PBS 0.5%Triton X-100 for 10 min at RT on a shaking device. Cells were washedwith PBS and blocking was performed with PBS 1% BSA for 45 min at RT.Incubation with the mouse monoclonal anti-Rep antibodies (Table 1) wasperformed for 1 h at 37° C. in PBS 1% BSA with 1:500 antibody dilutions(controls lacking primary antibodies were included). Cells were washedthree times with PBS followed by incubation with PBS 1% BSA for 15 minat RT. Then, incubation with the secondary antibody (AlexaFluor488 goatanti-mouse, 1:500; DNA marker Hoechst 33342, 1:5.000) was performed for45 min at RT in PBS 1% BSA. Cells were washed three times with PBS 1%BSA and three times with PBS prior to mounting with cover slips (Dakomounting medium). Immunofluorescence images were taken on a Zeiss CellObserver (20× objective, fixed exposure time for sample and controldublets).

The immunofluorescence images (FIG. 6 ) show that antibody treatmentwith group A and C antibodies leads to specific detection ofcytoplam+nuclear membrane (+nucleus)-localized target protein withoutdetection of aggregates. In contrast, group B and D antibodies showspecific colocalization with speckled protein and no to weak levels ofcytoplasmatic signals. The control incubation of the antibodies on theZsGreen fusion protein alone did not result in significant signaldetection (same exposition times used for visualization of the antibodysignals).

Example 8: Western Blot Analysis

HEK293TT (1.5 Mio/6-well) were cultured for 24 h in 6-well cell cultureplates in DMEM 10% FCS (supplemented with 1× Glutamax (Gibco) and 1×non-essential amino acids (Gibco)) followed by DNA transfection withpolyethylenimine (PEI) of ZsGreen1CI plasmids coding for overexpressionof the full length MSBI1, CMI1 or MSBI2 Rep protein as fusion proteinwith an N-terminal ZsGreen tag. 48 hours after DNA transfection, cellswere washed with PBS, detached by trypsination, washed again with PBSand lysed in SDS-PAGE Lämmli buffer (boil for 5 min at 98° C.). Thesamples were loaded onto precast 12.5% SDS-PAGE gels with one largepocket. After transferblot, each two stripes of the membrane were cutfor individual incubation of the stripes with the different mousemonoclonal antibodies of Table 1 (1:1000 dilution in PBS 5% skim milk)after blocking with PBS 5% skim milk. The stripes were washed threetimes with PBS 0.1% polysorbate (Tween®) 20 and incubated with theHRP-coupled anti-mouse secondary antibody allowing Westernblot analysisof antibodies detecting the different ZsGreen-Rep fusion proteins on aBiorad ChemiDoc device. Positive control detection was performed basedon incubation with a ZsGreen antibody (OriGene, 1:2000).

FIG. 7 shows while antibodies of the groups A and B specifically detectall three Rep fusion proteins, including the CMI1 and MSBI2 Rep fusionproteins in addition to the MSBI1 Rep fusion protein, the MSBI1-specificantibodies of group C and D exclusively detect the MSBI1 Rep fusionprotein. Antibody D2 is WB-negative most likely due to detection of a 3Dstructure epitope, which is not prevailed under denaturing condition inSDS-PAGE and was not tested here.

Sequence Summary

SEQ ID NO SEQUENCE 1Amino acid sequence of Rep protein encoded by MSBI1.176MSDLIVKDNALMNASYNLALVEQRLILLAIIEARETGKGINANDPLTVHASSYINQFNVERHTAYQALKDACKDLFARQFSYQEKRERGRINITSRWVSQIGYMDDTATVEIIFAPAVVPLITRLEEQFTQYDIEQISGLSSAYAVRMYELLICWRSTGKTPIIELDEFRKRIGVLDTEYTRTDNLKMRVIELALKQINEHTDITASYEQHKKGRVITGFSFKFKHKKQNSDKTPKNSDSSPRIVKHSQIPTNIVKQPENAKMSDLEHRASRVTGEIMRNRLSDRFKQGDESAIDMMKRIQSEIITDAIADQWESKLEEFGVVF 2Amino acid sequence of Rep peptide fragment EARETGKGINANDPLTVH 3Amino acid sequence of Rep peptide fragment KQINEHTDITASYEOHKKGRT 4His-Tag (with two neutral stuffer amino acids) GAHHHHHH 5 T7-TagMASMTGGQQMG 6 FLAG-Tag DYKDDDDK 7 Strep-II-Tag WSHPQFEK 8Amino acid sequence of Rep protein encoded by MSBI2.176MSKLVVKDNALMNASYNLDLVEQRLILLAIIEARESGKGINANDPLTVHAESYINQFGVHRVTAYQALKDACDNLFARQFSYQSKSEKGNIQNHRSRWVSEIIYIDTEATVKIIFAPAIVPLITRLEEQFTKYDIEQISDLSSAYAIRLYELLICWRSTGKTPIIGLGEFRNRVGVLDSEYHRIAHLKERVIEHSIKQINEHTDITATYEQHKKGRTITGFSFKFKQKKPKQAEIATETPKTATNDPDTTKPLTEPQIAKYSMILCKLGSISDLSNFPDYPAFANWIGNILRNPEKADEQ IAKRIFTALKTETDYSKKN 9MSBI.1 specific epitope NRLSDRF 10Amino acid sequence of Rep protein encoded by CMI1.252MSDLIVKDNALMNASYNLALVEQRLILLAILEARETGKGINANDPLTVHASSYINQFNVERHTAYQALKDACKDLFARQFSYQEKRERGRINITSRWVSQIGYMDDTATVEIIFAPAVVPLITRLEEQFTQYDIEQISELSSAYAVRLYELLICWRSTGKTPIIDLTEFRKRLGVLDTEYTRTDNLKMRVIELGLKQINEHTDITASYEQHKKGRTITGFSFKFKQKKKTGAEMPKNSDSSPHIEKPSQIPANIAKQPENAKKDDLGHRASKITGLIMSNGLADRFKRGDESVIDMMKRIKEEITTDTTADQWENKLEEFGVIFQS 11Amino acid sequence of Rep protein encoded by CMI2.214MSDLIVKDNALMNASYNLDLVEQRLILLAILEARETGKGINANDPLTVHAESYINQFGVARQTAYQALKDACKDLFARQFSYQEKRERGRANITSRWVSQIAYIDETATVEVIFAPAVVPLITRLEEQFTQYDIEQISGLSSAYAVRLYELLICWRSTGKTPVIELAEFRKRLGVLNDEYTRSDNFKKWIIENPIKQINEHTDITASYEQHKKGRTITGFSFKFKQKKKTEPETPKNSDSSQRIEKPSQIPANIVKQPENANLSDLQHRASKITGLIMSNRLSDRFKQGDESIMQMMARIQSEITTDSIADQWQSKLEEFGVVF 12Amino acid sequence of Rep protein encoded by CMI3.168MSDLIVKDNALMNASYNLALVEQRLILLAILEARETGKGINANDPLTVHASSYINQFNVERHTAYQALKDACKDLFARQFSYQEKRERGRANITSRWVSQIAYIDETATVEVIFAPAVVPLITRLEEQFTQYDIEQISGLSSAYAVRLYELLICWRTTGKTPVLDLTEFRKRLGVLDTEYTRTDNLKMRVIEQSLKQINKHTDITASYEQHKKGRTITGFSFKFQKKKTEPETPKNNDSGVSKPKTVEIPAEVVKQPKNTNLSDLEKRVRMITGAIAKNNLASRFQHGNESPLDMMKRIQSEITSDETADLWQNKLESMGV VF 13DNA sequence MSBI1 Rep codon-optimizedATGAGCGACCTGATCGTGAAAGACAATGCCCTGATGAACGCCTCCTACAACCTGGCACTGGTCGAACAGAGACTGATTCTGCTGGCTATCATCGAGGCAAGGGAGACCGGCAAGGGCATCAACGCCAATGACCCCCTGACAGTGCACGCCAGCTCCTACATCAACCAGTTTAATGTGGAGCGCCACACCGCCTATCAGGCCCTGAAGGACGCCTGCAAGGATCTGTTTGCCCGGCAGTTCAGCTACCAGGAGAAGCGGGAGAGAGGCAGGATCAACATCACAAGCAGATGGGTGTCCCAGATCGGCTATATGGACGATACCGCCACAGTGGAGATCATCTTTGCACCAGCAGTGGTGCCTCTGATCACCAGGCTGGAGGAGCAGTTCACACAGTACGACATCGAGCAGATCTCCGGACTGTCTAGCGCCTACGCCGTGCGCATGTATGACTGCTGATCTGTTGGCGGTCTACCGGCAAGACACCTATCATCGAGCTGGATGAGTTCCGCAAGCGGATCGGCGTGCTGGACACCGAGTACACCAGAACAGATAACCTGAAGATGAGAGTGATCGAGCTGGCCCTGAAGCAGATCAATGAGCACACCGATATCACAGCCTCTTATGAGCAGCACAAGAAGGGCCGCGTGATCACCGGCTTCAGCTTTAAGTTCAAGCACAAGAAGCAGAACTCTGACAAGACACCAAAGAATAGCGATTCCTCTCCCCGGATCGTGAAGCACAGCCAGATCCCTACCAACATCGTGAAGCAGCCAGAGAATGCCAAGATGTCCGACCTGGAGCACAGGGCATCTAGGGTGACAGGCGAGATCATGAGAAATAGGCTGAGCGATCGGTTCAAGCAGGGCGACGAGTCCGCCATCGATATGATGAAGAGAATCCAGTCCGAGATCATCACCGACGCCATCGCCGATCAGTGGGAATCTAAACTGGAAGAGTTTGGAGTCGTGTTTGGAGCACATCACCATCATCATCACTGA 14Protein sequence MSBI1 Rep codon-optimizedMSDLIVKDNALMNASYNLALVEQRLILLAIIEARETGKGINANDPLTVHASSYINQFNVERHTAYQALKDACKDLFARQFSYQEKRERGRINITSRWVSQIGYMDDTATVEIIFAPAVVPLITRLEEQFTQYDIEQISGLSSAYAVRMYELLICWRSTGKTPIIELDEFRKRIGVLDTEYTRTDNLKMRVIELALKQINEHTDITASYEQHKKGRVITGFSFKFKHKKQNSDKTPKNSDSSPRIVKHSQIPTNIVKQPENAKMSDLEHRASRVTGEIMRNRLSDRFKQGDESAIDMMKRIQSEIITDAIADQWESKLEEFGVVFGA 15DNA sequence MSBI1 Rep wild-typeATGAGCGATTTAATAGTAAAAGATAACGCCCTAATGAATGCTAGTTATAACTTAGCTTTGGTTGAACAGAGGTTAATTCTATTAGCAATCATAGAAGCGAGAGAAACAGGCAAAGGGATTAATGCCAATGATCCTTTAACAGTTCATGCAAGTAGCTATATCAATCAATTTAACGTAGAAAGGCATACGGCATATCAAGCCCTCAAAGATGCTTGTAAAGACTTGTTTGCCCGTCAATTCAGTTACCAAGAAAAGCGAGAACGAGGACGAATTAATATTACAAGTCGATGGGTTTCGCAAATTGGCTATATGGACGATACAGCAACCGTTGAGATTATTTTTGCCCCTGCGGTTGTTCCTCTGATTACACGGCTAGAGGAACAGTTCACCCAGTACGATATTGAGCAAATTAGCGGTTTATCGAGTGCATATGCTGTTCGTATGTACGAACTGCTGATTTGTTGGCGTAGCACAGGCAAAACACCAATTATTGAGCTAGACGAGTTTAGAAAGCGAATAGGTGTTTTAGATACTGAATACACTAGAACAGATAATTTAAAGATGCGAGTTATTGAATTAGCCCTAAAACAAATCAACGAACATACAGACATCACAGCAAGCTATGAACAACACAAAAAAGGGCGAGTGATTACAGGATTCTCATTCAAGTTTAAGCACAAGAAACAAAACAGCGATAAAACGCCAAAAAATAGCGATTCTAGCCCACGTATCGTAAAACATAGTCAAATCCCTCCAACATTGTAAAACAGCCTGAAAACGCCAAAATGAGCGATTTAGAACATAGAGCGAGCCGTGTTACAGGGGAAATAATGCGAAATCGTCTGTCAGATCGGTTTAAACAAGGCGATGAATCAGCAATCGACATGATGAAACGTATTCAAAGTGAAATAATAACCGATGCAATAGCAGACCAGTGGGAAAGCAAACTGGAGGAGTTTGGCGTGGTTT TTTAG

REFERENCES

-   Funk, M., et al. (2014). “Isolation of protein-associated circular    DNA from healthy cattle serum”. Genome Announc 2(4)-   Giraldo, R., et al. (2011). “RepA-WH1 prionoid: a synthetic amyloid    proteinopathy in a minimalist host.” Prion 5(2):60-64-   Gunst, K., et al. (2014). “Isolation of bacterial plasmid-related    replication-associated cirular DNA from a serum sample of a multiple    sclerosis patient.” Genome Announc 2(4).-   Lamberto, I., et al. (2014). “Mycovirus-like DNA virus sequences    from cattle serum and human brain and serum samples from multiple    sclerosis patients.” Genome Announc 2(4).-   Manuelidis L., 2011. “Nuclease resistant circular DNAs co-purify    with infectivity in scrapie and CJD”. J. Neurovirol. 17:131-145.-   Torreira, E., et al. (2015). “Amyloidogenesis of bacterial prionoid    RepA-WH1 recaptiulates dimer to monomer transitions of RepA in DNA    replication initiation.” Structure 23(1):183-189-   Whitley, C., et al. (2014). “Novel replication-competent cirulara    DNA molecules from healthy cattle serum and milk and multiple    sclerosis-affected human brain tissue.” Genome Announc 2(4).

The invention is further described by the following numbered paragraphs:

1. A DNA-replication-associated (Rep) protein for use in the diagnosisof multiple sclerosis (MS), wherein

-   -   (a) an at least 2-fold increased amount of Rep protein or        fragments thereof in a sample from a subject as compared to an        amount in a control sample; or    -   an at least 2-fold increased amount of anti-Rep antibodies in a        sample from a subject as compared to an amount in a control        sample correlates with a diagnosis of MS; and    -   (b) the Rep protein comprises    -   (i) an amino acid sequence as depicted in SEQ ID NO:1;    -   (ii) a fragment of SEQ ID NO:1 which is capable of binding an        anti-Rep antibody specific for a protein having the amino acid        sequence of SEQ ID NO 1; or    -   (iii) an amino acid sequence having a 90% or more homology to        the amino acid sequence of (i) or (ii) and is capable of binding        an anti-Rep antibody specific for a protein having an amino acid        sequence of SEQ ID NO:1.

2. The Rep protein of paragraph 1, wherein the fragment of SEQ ID NO:1comprises an epitope within the amino acid sequence consisting of aminoacids 1 to 229 of SEQ ID NO:1.

3. The Rep protein of paragraph 1 or 2, wherein an increased amount ofRep protein or fragments thereof or anti-Rep antibodies of at least5-fold as compared to a control sample indicates MS.

4. The Rep-protein of paragraph 1, wherein the protein is encoded by apolynucleotide acid as depicted in SEQ ID NO:13.

5. An anti-Rep antibody selected from the group consisting of antibodyAB01 523-1-1 (DSM ACC3327), antibody AB02 304-4-1 (DSM ACC3328),antibody MSBI1 381-6-2 (DSM ACC3329), antibody MSBI1 761-5-1 (DSMACC3330) and antibody MSBI1 961-2-2.

6. Use of an anti-Rep antibody of paragraph 5 in a method of any one ofparagraphs 1 to 4.

7. A method of diagnosing MS in a subject comprising the steps of

-   -   (a) incubating a sample from a subject with Rep protein as        defined in (b) of paragraph 1;    -   (b) detecting the amount of antibodies in the sample from the        subject forming an immunological complex with Rep protein; and    -   (c) correlating an at least 2-fold increased amount of antibody        bound to Rep protein in the sample from the subject, as compared        to an amount in a control sample, with a diagnosis of MS.

8. The method of paragraph 7, wherein in step (a) the Rep protein isimmobilized followed by incubating the immobilized Rep protein with thesample from the subject.

9. The method of paragraph 7, wherein in step (a) the Rep protein isexpressed in cells followed by incubating the cells with the sample fromthe subject.

10. The method of paragraph 8 or 9, wherein in step (b) the amount ofantibodies forming an immunological complex with Rep protein isquantified by a detecting binding agent coupled to a signal generatingcompound.

11. The method of paragraph 7, wherein in step (a) the antibodies in thesample from the subject are immobilized followed by incubating with adefined amount of Rep protein.

12. The method of any one of paragraphs 7 to 11, wherein the sample fromthe subject is a serum or a plasma sample.

13. A method of diagnosing MS in a patient comprising the steps of

-   -   (a) detecting the amount of Rep protein in a sample from a        subject by anti-Rep antibodies that bind to an epitope comprised        by SEQ ID NO:2 or SEQ ID NO:3, and    -   (b) correlating an at least 2-fold increased amount of Rep        protein detected in the sample from a subject in step (a) as        compared to an amount in a control sample with a diagnosis of        MS.

14. The method of paragraph 13, wherein the antibody specific for Repprotein binds to an epitope that is within an amino acid sequenceselected from the group consisting of amino acids from 1 to 136, from137 to 229 and from 230 to 324 of SEQ ID NO:1.

15. The method of paragraph 13 or 14, wherein the sample from a subjectis selected from the group consisting of a serum sample, plasma sampleor tissue sample.

16. A kit for use in the diagnosis of MS comprising

-   -   (a) a Rep protein, wherein the Rep protein comprises:    -   (i) an amino acid sequence as depicted in SEQ ID NO:1;    -   (ii) a fragment of SEQ ID NO:1 which is capable of binding an        anti-Rep antibody with specificity for a protein having the        amino acid sequence of SEQ ID NO: 1; or    -   (iii) an amino acid sequence having a 90% or more homology to        the amino acid sequence of (i) or (ii) and is capable of binding        an anti-Rep antibody with specificity for a protein having the        amino acid sequence of SEQ ID NO:1,    -   (b) an anti-human antibody coupled to a detectable label and        capable of binding to anti-Rep antibody with specificity for a        protein having the amino acid sequence of SEQ ID NO: 1, and    -   (c) a solid matrix suitable for immobilizing a Rep protein        according to (a) or anti-Rep antibodies with specificity for a        protein having the amino acid sequence of SEQ ID NO: 1 suspected        in a serum or plasma sample.

17. The kit according to paragraph 16 for use in an assay selected fromthe group consisting of enzyme-linked immunosorbent assay (ELISA),radioimmunoassay (RIA), enzyme immune assay (EIA), fluorescenceimmunoassay (FIA), luminescence immunoassay (LIA) and strip assay.

Having thus described in detail preferred embodiments of the presentinvention, it is to be understood that the invention defined by theabove paragraphs is not to be limited to particular details set forth inthe above description as many apparent variations thereof are possiblewithout departing from the spirit or scope of the present invention.

What is claimed is:
 1. An antibody specific for aDNA-replication-associated (Rep) protein selected from the groupconsisting of an antibody produced by hybridoma AB01 523-1-1 (DSMACC3327), an antibody produced by hybridoma AB02 304-4-1 (DSM ACC3328),an antibody produced by hybridoma MSBI1 381-6-2 (DSM ACC3329), anantibody produced by hybridoma MSBI1 761-5-1 (DSM ACC3330) and anantibody produced by hybridoma MSBI1 961-2-2 (DSM ACC3331).
 2. Theantibody of claim 1, wherein the antibody specifically binds to anepitope comprised by an amino acid molecule selected from the groupconsisting of SEQ ID NO: 2, 3 and
 9. 3. A method of diagnosing multiplesclerosis (MS) in a human patient comprising the steps of (a) incubatinga sample from the patient with an antibody of claim 1 (b) detecting theamount of Rep protein in the sample forming an immunological complexwith the antibodies, wherein the Rep protein comprises, (i) an aminoacid as depicted in SEQ ID NO: 1; (ii) a fragment of an amino acidsequence as depicted in SEQ ID NO: 1 which comprises an amino acidselected from the group consisting of amino acids 1 to 229 of SEQ ID NO:1 and SEQ ID NOS: 2, 3 or 9; or 8; or (iii) an amino acid sequencehaving a 90% or more identity to the amino acid sequence as depicted inSEQ ID NO: 1 and comprises the amino acid selected from the groupconsisting of amino acids 1 to 229 of SEQ ID NO: 1 and SEQ ID NOS: 2, 3or 9; and (c) correlating an at least 2-fold increased amount of Repprotein detected in the sample from a subject in step (b) as compared toan amount in a control sample with a diagnosis of MS.
 4. The method ofclaim 3, wherein the sample from the patient is selected from the groupconsisting of a serum sample, plasma sample or tissue sample.
 5. Themethod of claim 3 comprising an assay selected from the group consistingof enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA),enzyme immune assay (EIA), fluorescence immunoassay (FIA), luminescenceimmunoassay (LIA) and strip assay.
 6. The method of claim 3, wherein instep (b) the amount of Rep protein forming an immunological complex withthe antibodies is quantified by a detecting binding agent coupled to asignal generating compound.